单选题
If each side of △ACD above has length 3 and if AB has length 1, what is the area of region BCDF?
If each side of △ACD above has length 3 and if AB has length 1, what is the area of region BCDF?
【正确答案】
B
【答案解析】[解析] 由图可知BCDF的面积等于△ACD的面积减去△ABF的面积。因为△ACD是等边三角形，所以∠A=60°，△ABF是直角三角形，所以[*]，因此△ABF的面积=[*]；AACD的面积=[*]AC·AD·sin[*]；综上所述BCDF的面积为：[*]。